Operation of a traditional rectifying column, including a film column, consists in that the wet reflux flow made in a refluxer out of the heat and mass exchange zone between steam and liquid, is brought to the top of the column. Thus, as shown in FIG. 1, the vapor flow G and liquid reflux flow L is constant on all height levels of a column. The flow of the liquid reflux flow L usually considerably exceeds the flow of a distillate sampling P.